Patent literature 1: JP 2013-001152 A (corresponding to US 2012/0312604 A1)
For example, Patent literature 1 discloses a vehicular occupant determination apparatus which determines a type of an occupant on a vehicle seat in order to operate an occupant protection apparatus such as an airbag apparatus, a seatbelt pre-tensioner. In order to determine whether the occupant protection apparatus operates or not, this kind of the occupant determination apparatus determines which situations including a case where (i) there is nothing on a vehicle seat (also, referred to as a vacant seat, or vacant), (ii) a child restraint system (also referred to as CRS or a car seat) is fixed, (iii) a small-sized adult has a seat, or (iv) a large-sized adult has a seat. Hereinafter, by including the above situations regarding the vehicle seat determined by the occupant determination apparatus, the situations are named as an occupant type (also referred to as a type of an occupant).
In an occupant determination apparatus disclosed conventionally, a pair of front and rear load sensors is provided at a left-side support portion of the vehicle seat. In addition, the occupant determination apparatus determines the occupant type only when a detection value of an acceleration sensor which detects an acceleration of a lateral direction (also referred to as a vehicle width direction or a width direction of a vehicle) of a vehicle is equal to or less than a predetermined threshold. That is, the occupant type is not determined in a vehicle when the acceleration in the vehicle width direction exceeds the threshold. An occupant position or an occupant posture on the vehicle seat may change when acceleration occurs in the vehicle width direction according to a turning driving of the vehicle or the like. In this case, although the occupant type on the vehicular sheet has not changed, it may be determined that the occupant type has changed. In a conventional occupant determination apparatus, it may be possible to erroneously determine the occupant type due to the acceleration generated in the vehicle width direction.
The inventors of the present application have found the following regarding the conventional occupant determination apparatus. According to the conventional occupant determination apparatus, the determination of the occupant type is not performed when the acceleration in the vehicle width direction exceeds the threshold value. Thus, when the occupant type on the vehicle seat has changed in actual, the determination of the occupant type may be delayed. Especially, it is supposed that an adult sits on a vehicle seat which has been vacant when the vehicle stops at a road inclined in the vehicle width direction. In this case, the determination of a vacant seat state may remain before the vehicle drives and travels a flat road.